The primary objective is to relate changes in isoenzymes or other proteins which exist in multiple molecular forms and which are revelant to cancer chemotherapy, to the development of tumor cell resistance; multiple molecular forms of activating proteins identified in animal tumors will be confirmed in human tumors. The results of this study will also give information relative to the problem of predicting the sensitivity of tumors to chemotherapeutic agents. The initial studies will focus on uridine kinase and the glucocorticoid binding proteins.